diff options
Diffstat (limited to 'manual/manual.of')
| -rw-r--r-- | manual/manual.of | 124 |
1 files changed, 54 insertions, 70 deletions
diff --git a/manual/manual.of b/manual/manual.of index 8a8ebad5..b7ced443 100644 --- a/manual/manual.of +++ b/manual/manual.of @@ -594,7 +594,7 @@ controls how long the collector waits before starting a new cycle. The collector starts a new cycle when the use of memory hits @M{n%} of the use after the previous collection. Larger values make the collector less aggressive. -Values smaller than 100 mean the collector will not wait to +Values less than 100 mean the collector will not wait to start a new cycle. A value of 200 means that the collector waits for the total memory in use to double before starting a new cycle. @@ -608,7 +608,7 @@ how many elements it marks or sweeps for each kilobyte of memory allocated. Larger values make the collector more aggressive but also increase the size of each incremental step. -You should not use values smaller than 100, +You should not use values less than 100, because they make the collector too slow and can result in the collector never finishing a cycle. The default value is 100; the maximum value is 1000. @@ -1004,7 +1004,7 @@ the escape sequence @T{\u{@rep{XXX}}} (note the mandatory enclosing brackets), where @rep{XXX} is a sequence of one or more hexadecimal digits representing the character code point. -This code point can be any value smaller than @M{2@sp{31}}. +This code point can be any value less than @M{2@sp{31}}. (Lua uses the original UTF-8 specification here.) Literal strings can also be defined using a long format @@ -1370,73 +1370,49 @@ because now @Rw{return} is the last statement in its (inner) block. The @Rw{for} statement has two forms: one numerical and one generic. +@sect4{@title{The numerical @Rw{for} loop} + The numerical @Rw{for} loop repeats a block of code while a -control variable runs through an arithmetic progression. +control variable goes through an arithmetic progression. It has the following syntax: @Produc{ @producname{stat}@producbody{@Rw{for} @bnfNter{Name} @bnfter{=} exp @bnfter{,} exp @bnfopt{@bnfter{,} exp} @Rw{do} block @Rw{end}} } -The @emph{block} is repeated for @emph{name} starting at the value of -the first @emph{exp}, until it passes the second @emph{exp} by steps of the -third @emph{exp}. -More precisely, a @Rw{for} statement like -@verbatim{ -for v = @rep{e1}, @rep{e2}, @rep{e3} do @rep{block} end -} -is equivalent to the code: -@verbatim{ -do - local @rep{var}, @rep{limit}, @rep{step} = tonumber(@rep{e1}), tonumber(@rep{e2}), tonumber(@rep{e3}) - if not (@rep{var} and @rep{limit} and @rep{step}) then error() end - @rep{var} = @rep{var} - @rep{step} - while true do - @rep{var} = @rep{var} + @rep{step} - if (@rep{step} >= 0 and @rep{var} > @rep{limit}) or (@rep{step} < 0 and @rep{var} < @rep{limit}) then - break - end - local v = @rep{var} - @rep{block} - end -end -} - -Note the following: -@itemize{ - -@item{ -All three control expressions are evaluated only once, -before the loop starts. -They must all result in numbers. -} - -@item{ -@T{@rep{var}}, @T{@rep{limit}}, and @T{@rep{step}} are invisible variables. -The names shown here are for explanatory purposes only. -} - -@item{ -If the third expression (the step) is absent, -then a step @N{of 1} is used. -} - -@item{ -You can use @Rw{break} and @Rw{goto} to exit a @Rw{for} loop. -} - -@item{ -The loop variable @T{v} is local to the loop body. +The given identifier (@bnfNter{Name}) defines the control variable, +which is local to the loop body (@emph{block}). + +The loop starts by evaluating once the three control expressions; +they must all result in numbers. +Their values are called respectively +the @emph{initial value}, the @emph{limit}, and the @emph{step}. +If the step is absent, it defaults @N{to 1}. +Then the loop body is repeated with the value of the control variable +going through an arithmetic progression, +starting at the initial value, +with a common difference given by the step, +until that value passes the limit. +A negative step makes a decreasing sequence; +a step equal to zero raises an error. +If the initial value is already greater than the limit +(or less than, if the step is negative), the body is not executed. + +If both the initial value and the step are integers, +the loop is done with integers; +in this case, the range of the control variable is limited +by the range of integers. +Otherwise, the loop is done with floats. +(Beware of floating-point accuracy in this case.) + +You should not change the value of the control variable +during the loop. If you need its value after the loop, assign it to another variable before exiting the loop. -} -@item{ -The values in @rep{var}, @rep{limit}, and @rep{step} -can be integers or floats. -All operations on them respect the usual rules in Lua. } -} +@sect4{@title{The generic @Rw{for} loop} + The generic @Rw{for} statement works over functions, called @def{iterators}. @@ -1499,6 +1475,8 @@ then assign them to other variables before breaking or exiting the loop. } +} + @sect3{funcstat| @title{Function Calls as Statements} To allow possible side-effects, function calls can be executed as statements: @@ -1819,7 +1797,7 @@ A comparison @T{a > b} is translated to @T{b < a} and @T{a >= b} is translated to @T{b <= a}. Following the @x{IEEE 754} standard, -@x{NaN} is considered neither smaller than, +@x{NaN} is considered neither less than, nor equal to, nor greater than any value (including itself). } @@ -2171,7 +2149,7 @@ then the function returns with no results. @index{multiple return} There is a system-dependent limit on the number of values that a function may return. -This limit is guaranteed to be larger than 1000. +This limit is guaranteed to be greater than 1000. The @emphx{colon} syntax is used for defining @def{methods}, @@ -2367,7 +2345,7 @@ but it also can be any positive index after the stack top within the space allocated for the stack, that is, indices up to the stack size. (Note that 0 is never an acceptable index.) -Indices to upvalues @see{c-closure} larger than the real number +Indices to upvalues @see{c-closure} greater than the real number of upvalues in the current @N{C function} are also acceptable (but invalid). Except when noted otherwise, functions in the API work with acceptable indices. @@ -2879,7 +2857,7 @@ Ensures that the stack has space for at least @id{n} extra slots (that is, that you can safely push up to @id{n} values into it). It returns false if it cannot fulfill the request, either because it would cause the stack -to be larger than a fixed maximum size +to be greater than a fixed maximum size (typically at least several thousand elements) or because it cannot allocate memory for the extra space. This function never shrinks the stack; @@ -4053,7 +4031,7 @@ for the @Q{newindex} event @see{metatable}. Accepts any index, @N{or 0}, and sets the stack top to this index. -If the new top is larger than the old one, +If the new top is greater than the old one, then the new elements are filled with @nil. If @id{index} @N{is 0}, then all stack elements are removed. @@ -5056,7 +5034,7 @@ size @id{sz} with a call @T{luaL_buffinitsize(L, &b, sz)}.} @item{ Finish by calling @T{luaL_pushresultsize(&b, sz)}, where @id{sz} is the total size of the resulting string -copied into that space (which may be smaller than or +copied into that space (which may be less than or equal to the preallocated size). } @@ -7336,7 +7314,7 @@ Functions that interpret byte sequences only accept valid sequences (well formed and not overlong). By default, they only accept byte sequences that result in valid Unicode code points, -rejecting values larger than @T{10FFFF} and surrogates. +rejecting values greater than @T{10FFFF} and surrogates. A boolean argument @id{nonstrict}, when available, lifts these checks, so that all values up to @T{0x7FFFFFFF} are accepted. @@ -7572,7 +7550,7 @@ returns the arc tangent of @id{y}. @LibEntry{math.ceil (x)| -Returns the smallest integral value larger than or equal to @id{x}. +Returns the smallest integral value greater than or equal to @id{x}. } @@ -7597,7 +7575,7 @@ Returns the value @M{e@sp{x}} @LibEntry{math.floor (x)| -Returns the largest integral value smaller than or equal to @id{x}. +Returns the largest integral value less than or equal to @id{x}. } @@ -7611,7 +7589,7 @@ that rounds the quotient towards zero. (integer/float) @LibEntry{math.huge| The float value @idx{HUGE_VAL}, -a value larger than any other numeric value. +a value greater than any other numeric value. } @@ -8352,7 +8330,7 @@ of the given thread: @N{level 1} is the function that called @id{getinfo} (except for tail calls, which do not count on the stack); and so on. -If @id{f} is a number larger than the number of active functions, +If @id{f} is a number greater than the number of active functions, then @id{getinfo} returns @nil. The returned table can contain all the fields returned by @Lid{lua_getinfo}, @@ -8746,6 +8724,12 @@ When needed, this metamethod must be explicitly defined. } @item{ +The semantics of the numerical @Rw{for} loop +over integers changed in some details. +In particular, the control variable never wraps around. +} + +@item{ When a coroutine finishes with an error, its stack is unwound (to run any pending closing methods). } |